02723nas a2200205 4500000000100000008004100001260001500042100001600057700001400073700001300087700001200100700001300112700001200125245019900137856005000336300001000386490000700396520210000403020001402503 2018 d c2018/01/051 aR. Dejardin1 aS. Kender1 aC. Allen1 aM. Leng1 aG. Swann1 aV. Peck00a\textquotedblleftLive\textquotedblright (stained) benthic foraminiferal living depths, stable isotopes, and taxonomy offshore South Georgia, Southern Ocean: implications for calcification depths uhttps://www.j-micropalaeontol.net/37/25/2018/ a25-710 v373 a
It\ is widely held that benthic foraminifera exhibit species-specific calcification depth preferences, with their tests recording sediment pore water chemistry at that depth (i.e. stable isotope and trace metal compositions). This assumed depth-habitat-specific pore water chemistry relationship has been used to reconstruct various palaeoenvironmental parameters, such as bottom water oxygenation. However, many deep-water foraminiferal studies show wide intra-species variation in sediment living depth but relatively narrow intra-species variation in stable isotope composition. To investigate this depth-habitat\textendashstable-isotope relationship on the shelf, we analysed depth distribution and stable isotopes of living
(Rose Bengal stained) benthic foraminifera from two box cores collected on the South Georgia shelf (ranging from 250 to 300m water depth). We provide a comprehensive taxonomic analysis of the benthic fauna, comprising 79 taxonomic groupings. The fauna shows close affinities with shelf assemblages from around Antarctica. We find live
specimens of a number of calcareous species from a range of depths in the sediment column. Stable isotope ratios (δ13C and δ18O) were measured on stained specimens of three species, Astrononion echolsi, Cassidulinoides porrectus, and Buccella sp. 1, at 1cm depth intervals within the downcore sediment sequences. In agreement with studies in deep-water settings, we find no significant intra-species variability in either δ13Cforam or δ18Oforam with sediment living depth on the South Georgia shelf. Our findings add to the growing evidence that infaunal benthic foraminiferal species calcify at a fixed depth. Given the wide range of depths at which we find living
, infaunal
species, we speculate that they may actually calcify predominantly at the sediment\textendashseawater interface, where carbonate ion concentration and organic carbon availability is at a maximum.